Secret transmission system



March 3, 1931. R. H. RANGER SECRET TRANSMISSION SYSTEM Filed April 21, 1928 7D TRANSMITTER 0k RECEIVER INVENTOR R. H RANGER j/NgYdW Patented Mar. 3, 1931 STATES PATENT OFFICE RICHARD HOWLAND RANGER, F NEWARK, NEW JERSEY, ASSIGNOR TO RADIO COR- PORATION OF AMERICA, A CORPORATION OF DELAWARE sncanr TRANSMISSION sYsTEM Application filed April 21,

The invention relates to a method and means for obtaining secret radio or wire transmission of messages such as code, pictures, stock quotations, facsimiles, finger prints, checks, documents, and the like over a plurality of signal channels connecting transmitting and receiving stations of ap-- propriate type for the particular transmission.

The invention further lends itself to the feature that a method and means is provided which renders listening in by undesired receiving stations or individuals diflicult, due to a varying rate of switching'between various signal channels connectin the transmitting and receiving stations. his switching between successive signal channels is preferabl carried on at a variable rate and, with eacli channel transmitting a separate and distinct message if a desired receiving station were hooked in with the line in case of wire transmission or tuned in to the particular transmitted frequency in the case of radio transmission, the station would 'be able to receive nothing more than a garbled message in which parts of two or more messages would be successively received. This garbling of the receivedmessage would make it impossible for the receiving station to distinguish between any of the several messages being transmitted. As a specific example, it might be stated, that the system consists in providing a method and means for changing the path ofcommunication between transmitting and receiving stations successively between a plurality of channels in a predetermined and prearranged order. For example, it might be supposed that there were two signal channels designated as A and B in whichchannel A was assigned to one message and channel B was assigned to another message, andif at a certain time intervals each of the two channels are simultaneously connected between both the transmitting and the receiving stations, it will be seen that the two messages continue to come through correctly, but, if any undesired station is attempting to receive the said messages as transmitted and does not know when the said interchanges between the chan- 1928. Serial No. 271,670.

message can not beireceived by the undesired I station due to the fact that the separate messages on the separate channels will be intermingled and garbled.

Also, if the invention be regarded as being drawn to a transmitting and receiving system for picture telegraphy and the like, for example, the same method may be applied to simplex operation of a single picture. In the case of simplex operation it might be advisable to transmit current for white portions of the picture and set the receiving mechanisms to record white for received signal energy. This consistency might be reversed according to a prearranged schedule after a certain period of time so that black would then be transmitted and recorded as the current impulses, and the operation would go on undisturbed. Anyone attempting to receive the picture who was unfamiliar with the schedule of changes between white and black would have extreme difliculty in following the various changes from white to black and vice versa.

It is, therefore, an object of my invention to provide a system for transmitting and receiving signals or pictures by wire or radio in which a plurality of transmission channels or lines may be used to connect the transmitter and receiver and in which an im proved method of obtaining secrecy of transmission, especially for multiplex work and simplex as above defined, is provided.

\ A further object of my invention is to provide a system which readily lends and adapts itself, in the case of picture transmission,

to use in transmitting either a plurality of velop a cipher wheel or disk which may be Composed of a cipher of any desired combination and, at the same time, provide a cipher which may readily be interchanged at both the transmitting and receiving station with another cipher for the purpose of obtaining additional secrecy.

Other objects of my invention are to provide in a manner hereinafter set forth, a-

secret communication system which issimple in its construction and arrangement, as well as durable, compact, conveniently operated, eflicient in its use, readily set up and inexpensively installed.

Still other objectsand advantages of my invention will be apparent after a detailed study of the following description and claims when read in connection with the accompanying drawing, wherein have illustrated by the single figure a conventional embodiment which shows the principles 'of my invention in diagrammatic form. It is to be distinctly understood that the various parts comprising the invention, as shown, are merely diagrammatic and that I am not to be restricted thereto, but that equivalent mechanical details may readily be substituted for those conventionally illustrated.

preferably forms the plus lead for channel A and the connection 3 forms the minus lead for the said channel. Similiarly, the connection 3 also forms the minus lead for channel B whose plus lead is designated as 5 and is connected with the connection 11 of the contact block 13. The arms 15 and 17 connected respectively with the contacts 7 and 11 extend outwardly from the block 13 and are bent at their ends to form a pointed connection to form a portion of a switching device, generally designated 19. The switching device-19, prefera 1 formed from a flexible material and exten ing from the contact block 13 and forming a connection with the contact member 9, extends as a vibrating tongue between the arms 15 and 17 and forms, depending upon its position, a closed circuit for either channel A or channel B through either of the arms 15 or 17.

For the purpose of illustration I have shown the contact block 13 mounted at the top of a standard or support 21 fastened to a base member 23. Carried by the support 21 is the electromagnet 25 with which is associated an armature 27 having its end 29 bent IL-shaped for a purpose of forming a follower to be hereinafter described. Likewise, associated with the contact device 19 is an extended rod 31 riveted or fastenedthereto at 33. The rod 31 extends between the contact device 19 and the upper portion of the armature 27 so that for an upward movement of the armature due to a force exerted by the magnet 25 the contact device 19 is lifted off the extended arm 17 and carried against the arm 15 to form a circuit through channel A, but upon the armature 27 being dropped the contact arm 19, due to the rod 31 following the armature 27, drops and forms a circuit for the channel B through the arm'17.

Likewise, mounted upon the base or supporting member 23 in a standard 33 is a shaft 35 carrying a cipher disk or wheel generally designated 37. The cipher disk 37 is rigidly mounted upon the shaft 35 and rotates thereon in the usual manner for the purpose to be hereinafter described. Upon the periphery of the cipher disk or wheel 37 and extending a distance along the periphery thereof hearing a fixed ratio to a predetermined division of the periphery of the cipher wheel is the cipher which will determine the secrecy of operation. In the case shown, for example, the division is into twelve parts of which part a represents one division. The cipher preferably consists of raised portions designated 41, 41a, 41?) etc. and depressed portions designated 43, 43a, 43?) etc. each of which extend for a certain distance along the periphery of the said cipher disk. In the case shown raised portion 41 extends for a distance which I have shown as a, the portion 43 for a distance a, the portion 41a for a distance 2a, the portion 43a for a distance-a, etc, so that the portion 29 of the armature 27 bent L-shaped to form a follower surface is raised and lowered to follow the cipher out upon the;

disk 37. In the case shown, the portions 41', 41a, 416, etc. will provide the cipher for determining the time and rate of operation of signal channel A and the depressed portions 43, 43a, 43?) etc. will form the ci her for controlling the time of operation of t e channel B, which, as has been above stated, are controlled due to the raising and lowering of the armature 27 and the resulting movement of the rod 31 up and down to change'the position of the contact device 19 between the contact arms 15 and 17 'F or the purpose of advancing the cipher disk or wheel in a direction as indicated by the arrow or, in other words, in a counterclockwise direction, as shown, a ratchet wheel 45 is likewise rigidly associated with the shaft 35 and by means of the teeth 47 and the lever arm 49, the ratchet wheel is periodically and interruptedly advanced. The advancement ers the follower 29 to periodically and interruptedly raise and lower the rod 31 in accordance with the contour of the periphery of the cipher disk 37, as formed by the raised and lowered portions 41 and 43, etc., respectively.

Supported from the base member 23 by a bracket arm 51 is an electromagnet 53 having a winding 55 and core 57. The winding 55 is included in the circuit of a battery 59 and, for the purpose of illustration, pendulum mechanism 61 and switch 63 are'shown as a means for periodically completing the circuit and then periodically openingthe same. This circuit, since it is for advancing the cipher disk will hereinafter be referred to as the advance circuit. The pendulum mechanism may, if desired, be of the seconds pendulum type so as to close the circuit including the magnetic winding, switch and battery at interrupted intervals of one second each, or, the pendulum may, if desired, be replaced by a contact upon the end of a reciprocating carriage for picture transmission of the type disclosed in my copending application, Serial No. 128,720, filed August 12, 1926, or Serial No. 235,431, filed November 25, 1927, each of which show reciprocating carriage members and, in this case, the switch 63 will be closed at each reciprocation of the carriage mechanism, or, as a still further modification upon each rotation of a spiral picture carrying element. It is believed that each of these modifications are clear and need no explanation by Way of drawings due to the fact that it is believed obvious that each reciprocation or rotation of a picture carrying surface might close a contact switch to change the position of the cipher disk. Of course, referring specifically to picture transmission systems the contact point or lug may be provided on the rotary recording drum which will close a circuit at each revolution of the said recording drum.

Each closure of the advance circuit through the pendulum orother equivalent device 61, the battery 59, the magnetic winding 55, and the switch 63 will energize the magnet 53 and magnetize its associated core 57 in such a manner as to draw the armature 65,

which is pivoted to a supporting member 67 at 69, to the left, as shown by the drawing, and thus bring the said armature 65 against the magnetized core against the force of a spring member 71. The lever arm 49 for advancing the ratchet mechanism is pivoted to the free end of the armature 65 at 73 and is held in a position tending to rotate the said lever arm counter-clockwise with respect to the armature 65, as shown, by a spring member 75.- However, this motion of the lever arm 49 is prevented by the fact that the said lever arm rests upon the end 77 of the supporting arm 51 which carries the magnet 53. The motion of the arm 49 to the right, as shown by the drawing, due to the force of the spring 71 upon the armature 65 when the circuit including the magnet 53 is opened by the switch 63 to demagnetize the core 57, is prevented by means of a lug 79 carried on the end side of the lever arm 49. The lug 79 is adapted to catch against the upper portion 77 of the upstanding arm 51. Upon each energization of the magnet 53 and resulting magnetization of the core 57 the lever arm 49 is drawn to the left, as shown, and the tooth 81 forming the end of lever 49 is pressed against the teeth 47 of the ratchet wheel so as to advance the same in the direction of the arrow. With the part 61 being in the form of a seconds pendulum, a synchronously driven recording or transmittin apparatus, or the equivalent, it is readily 0 served that the ratchet wheel 45 drives or rotates the shaft 45 at a fixed and predetermined rate of speed. It is, therefore, seen that the cipher disk likewise moves with the ratchet Wheel 45 and, therefore, the cipher out upon the periphery of the cipher disk 47 periodically opens and closes the signal channels A and B in accordance with the rate of raising and lowering of the follower 29.

For the purpose of starting the apparatus at both the transmitting and the receiving instrumentalities in a uniform position with respect to a definite signal channel and with respect to a definite point on the cipher wheel, a small motor, generally designated as 83, has its rotary 85 fastened to or made a part of the rotary shaft 35. The rotor 85 consists of a tromagnets 87 and 89 are of opposite polarity and maintain the rotor element in substantially the position shown by the drawing so that the north pole ofthe rotor, represented N, and the south pole of the stator, represents S, are in direct alignment and vice versa with respect to the south pole S of the permanent magnet and north pole N of the electromagnet. The winding 91 and 93 of the motor 83 are series connected with respect to themselves and to the electromagnet 25, which will hereinafter be designated the return magnet, and, in addition, form a part of the complete series connected return circuit which includes the windings 93 and 91 of the stator magnets, the winding for the return magnet 25, a battery 95, and switch 97. At a predetermined interval the operator at the transmitting and at the receiving station may throwthe switch 97 to a closed position so as is turned to a proper starting point from which starting operations may be commenced. Instead of having a switch 97 at both the transmitting and at the receiving station a line might be run, if desired, between two stations and a single switch provided so that when one operator was ready he could control.

both stations thus assuring accuracy although for predetermined times of operation accuracy of high degree is readily obtainable.

To now briefly rehearse the operation, it is seen that the starting. of the system is governed in accordance with the time of closing the switch 97 and thus positioning the cipher disk in its proper relationship and raising the armature 27 so as to turn the follower 29 to clear the disk. Upon again opening the switch 97, the magnets 25, 91 and 93 are deenergized, and, should the cipher disk 37 be in a position as indicated upon the drawings, the armature 27 and its follower 29 will immediately drop so that channel B is closed and for the instant a signal would be transmitted over this signal channel. At the same time the synchronously operating mechanisms at the transmitting and receiving stations, such as the seconds pendulum, or, in the case of picture transmission work, synchronously driven picture transmitting and receiving machines, periodically and at a fixed and predetermined rate close the switch 63 and the ad vance'circuit. The closure of the advance circuit will energize the magnet 53 at regular intervals so that the ratchet wheel 45 is stepped in a counter-clockwise direction, looking at the drawing, so that Various portions of the cipher disk influence the follower 29 to open or close the contacts of channels A or B by connecting either of the contact arms 15 and 17 with the joint contact element 19.

It is thus seen that I have provided an arrangement for continuously and successively.

switching from one to anotherof a plurality of signal channels at a fixed definite and predetermined rate and also provided a system in which both the receiving station and the transmitting station are simultaneously switched to the same signal channel. Thus, if a listener were to attempt to receive the message transmitted over channel A, for exam-- ple, he would be continually handicapped in the result which could be obtained by reason of the fact that for substantially half the time, in the case of two channel operations as shown, he would be receiving a different signal, or the same signal in reversed form from channel B although he was unfamiliar with the fact and the composite result of the message he received would be a badly garbled attempt at reception and a substantially unintelligible jumble of code or other signal pulses. It, therefore, appears that in order to obtain a correct understanding of the trans mitted message that the knowledge of the cipher employed at the transmitter is necessary at each receiving point.

While I have described my invention particularly in regard to'picture transmission and reception systems and designated the synchronously operated. elements or instrumentalities as picture carrying drums in which the light sensitive-element or recording element assumed either a rotary motion, a reciprocating motion, or both rotary and reciprocating motion, I do not intend to be associated therewith, or, I may modify the single cipher disk to provide a means for switching between three or more signal channels. Also in this specification and the appended claims it is to be understood that the term signal channels is intended to include all the existing means for securing communication either by separate transmission circuits or multiplex transmission on the'sa'me circuit. It is, therefore, to be understood that my invention is broad and capable of various modifications, and I am clearly entitled to make such changes from the diagrammatic showing herein made as fall fair-' ly within the spirit and scopeof myv invention as set forth in the following claims.

Having thus described my invention, what I claim is:

1. A transmission system including a plurality of signal channels, and means for continuously and interruptedly switching from one to another of said signal channels at'predetermined and variable time periods.

2. A communication system including a plurality of signal channels, means for successively switching from one to another of said signal channels, and means for varying the time period upon which switching between said signal channels takes place.

3. A communication system including a plurality ofsignal channels, means for sequentially switching from one to another of said channels,'means forcontrolling in accordance with a predetermined "cipher the time period at which switching from one to another of said channels takes place, and means for advancing said switch controlling means at a predetermined rate.

4. A communication system including a plurality of signal channels, means for sequentially energizing one of said signal chan nels and simultaneously deenergizing the re maining signal channels, and means for conof each of said signal channel's'in accordance with a predetermined cipher. v

5. A'communication system including a plurality of communication channels, means for switching from one to another of said communication channels, and a cipher disk for determining the rate of switching from one to another of said communication channels and varying the period of energization of any one of said communication channels.

6. A communication system including aplurality of signal channels, means for,

periodically switching the communication from one to another of said signalchannels, a disk having a cipher out upon its periphery for controlling the said switching means, and means for continually changing the said time the position of said disk and associated cipher with respect to said switching means at a fixed and predetermined rate so as to vary receiver, means provided at both said transmitter and receiver for continually and successively switching from one to another of said channels for different predetermined periods of time to change the operating time on the various connecting channels between said transmitter and receiver. 7

'10. A communication system including a transmitter and a receiver, a plurality of signal channels connecting said transmitter and receiver, means provided at both said transmitter and receiver for s equentially switching the connection of said transmitter to said receiver from one to another of said signal channels for different predetermined time periods of connection on each of said channels, and means for governing the time of of switching between signal said switching operation between said con necting signal channels for said transmitter and receiver at a synchronous rate.

11. A communication system including a transmitter and a receiver, a plurality-ofsignal channels connecting said-transmitter and receiver, means located at both said transmitter and receiver for successively and continuously switching the connection of said transmitter and receiver from one to another of said signal channels, a cipher disk located at both said transmitter and "said receiver for controlling the rate "of switching between said channels, and synchronously operating at said transmitter and receiver for continually changing the position of said cipher disk whereby variable time periods of transmission on the plurality of channels are ob tained. I

12. A communication system including a s transmitter and a receiver, a plurality of signal channels connecting said transmitter and said receiver,means for successively and continuously switching from one to another of said signal channels whereby said transmitno ter and receiver areconnected at any instant by only a single signal channel, a cipher disklocated at said transmitter and said receiver for controlling the time period at which switching between saidsignal channels takes place, and synchronously operated means at said transmitter and said receiver for advancing said cipher disk with respect to said switching means whereby synchronous switching is obtained.

13. A communication system including a transmitter and a receiver of substantially like characteristics, a plurality of signal channels connecting said transmitter and said receiver, means located at said transmitter and; 05 receiver for switching the connection between said transmitter and said receiver from one to another of said signal channels, a cipher disk associated with each of said switching means for continuously varying the time incessive signal channels are energized at predetermined time intervals at the transmitter and signals over said channels are received at like predetermined time intervals at th said receiver. V

14. A communication system including a transmitter and a receiver, a plurality of signal channels connecting said transmitter and receiver, means for switching the connec-. tion of said transmitter and receiver between said various signal channels, means located 1Ml nod at said transmitter and receiver for control ling the time interval between each switching operation between said various signal chansignal channels are synchronously maintained and signals transmitted over each individual signal channel are received at the variable time periods of transmission and the plurality of separate messages over the separate signal channels are clearly discernible.

1 5. A communication system including a transmitting and a receiving station, a plurality of signal channels connecting said. transmitting and said receiving stations, means for switching the connection of said stations between successive signal channels, a cipher disk associated with said switching means for controlling the same and varying the time intervals between which switching between successive signal channels occurs, means located at both said transmitting and said receiving stations for positioning said cipher in a fixed and predetermined relationship with respect to said switching means, and an electromagnetic controlled step-bystep means for advancing the said cipher disk at a predetermined ,raflze and continuously changing the position of said cipher upon means.

-.sponding to the time intervals 16. The method of obtaining secret communication and utilizing only a singlesignal channel at any instant which includes transmitting and receiving a message over a plurality of signal channels, switching the communication from one to another of said signal channels for variable predetermined time periods, and receiving the message over each of said signal channels in accordance with said variable time periods of transmission on each of said channels.

17. The method of obtaining communication with a plurality of signal channels which includes transmitting at interrupted intervals a plurality of messages over said plurality of signal channels, switching be- I tween said signal-channels and transmitting on one of said channels in accordance with 18. The method of communicating over a plurality of signal channels which includes transmitting and receivmg a plurality "of messages over a plurality of signal channels, synchronously switching the communication fromone to another of said signal channels connecting said transmitter'and receiver, synchronously varying the time interval between successlve swltching operations at said transmitter and receiver in accordance with a predetermined cipher, andpos'itioning said switching with respect to. a definite position of the said "cipher, whereby the rate of switching between successive chan- 'nels is varied in a fixed and predetermined relationship at both said transmitter and receiver.

RIC-HARD, HOAND RANGER.

' nee said switching, variably controlling the time period between successive switching operations at said transmitter, receiving messages over said plurality of signal channels, con-4 trolling the said receiving signal channels in accordance with the time period corre- Q switching between transmission channels, and continually and synchronously varying the switch- 

